Organ walls are composed of several layers: the mucosa (the inner surface layer), the submucosa, the muscularis (muscle layer), and the serosa (connective tissue layer). In cases of gastrointestinal, colonic, and esophageal cancer, for example, small polyps or cancerous masses may form along the mucosa and often extend into the lumens of the organs. Conventionally, that condition has been treated by cutting out or otherwise removing a portion of the affected organ wall. This procedure, however, often may cause extensive discomfort to patients and may pose health risks. Recently, physicians have adopted a minimally invasive technique known as endoscopic mucosal resection (EMR), which removes the cancerous or abnormal tissue while keeping the walls of the organ intact. EMR may also assist in removing any undesired tissue, even if such tissue is not abnormal or diseased.
EMR is generally performed with an endoscope, which, in some embodiments, may be a long, narrow elongated member having channels equipped with an illumination source, an imaging device, and/or other instruments. In some instances of EMR treatment, the endoscope may be passed down the throat, guided through the rectum, or passed through other natural body openings to reach the tissue targeted for resection. The distal end of the endoscope may further include a cutting guide (e.g., a cap) and a cutting device (e.g., a wire loop) introduced through an endoscopic channel towards the guide. Once there, suction may be applied through the elongate member, which draws the targeted tissue towards and into the cutting guide. Alternatively, the targeted tissue may be drawn into the cap by any suitable means. When the tissue is sufficiently drawn into the cap, the cutting device may close around the tissue, thereby resecting it from the organ wall. Subsequently, excised tissue may be extracted for examination, biopsy, or disposal.
In addition, conventional EMR caps may be circular, oblique, elliptical, or any combination thereof. These EMR caps may consequently have resection openings of similar geometries. During procedures where a large area of tissue is to be removed, separate circular cuts are generally utilized to remove the target tissue. However, due to the risk of perforating the underlying muscularis layer, caution is exercised and overlapping cuts are avoided. By avoiding overlapping circular cuts, areas between the adjacent circular cuts are often not removed. These areas of potentially undesired tissue may be left behind by the conventional circular EMR caps, may require additional procedures or contribute to the development of metastatic cancer, if the tissue left behind is diseased.
Therefore, there exists a need for an improved endoscopic mucosal resection tool that effectively resects targeted tissue without damaging the surrounding tissue or muscle layers of the organ; and that allows for more complete, efficient removal of larger areas of tissue.